Primary Investigators: Sophie St. Hilaire, Maya Groner

Non-native species threaten biodiversity and, in the oceans, can decrease the productivity of farmed and wild fisheries. While removal of non-natives is a common remediation approach, it does not guarantee that a site will return to its pre-disturbance state. If eradication or reduction of non-native species is not accompanied by mitigation strategies to increase population resiliency, a site may convert to an alternate stable state with decreased productivity.

In the north Atlantic, oysters and eelgrasses provide essential habitat for many ecologically and commercially important fisheries (e.g., halibut, soft-shelled clams, Rock crab, salmon, oysters, mussels). The non-native green crab (Carcinus maenus) may threaten these habitats by consuming molluscs, including reef-forming oysters, and by digging and degrading the quality of eelgrass beds. The resilience of these ecosystems to green crab disturbances is unknown.

We propose to quantify the impacts of green crabs on coastal marine habitats and evaluate the effects of a new green crab fishery on the recovery of these systems. Using field surveys along the existing gradient in green crab densities in PEI, we will test the hypotheses that: 1) Green crabs are reducing the densities and health of eelgrass beds; 2) Recovery of eelgrass density and health will be fastest when eelgrass and oysters are in close proximity; 3) Wasting disease (WD) is inhibiting the recovery of eelgrasses; and, 4) WD prevalence is greater where oysters do not co-occur.